1. Field of the Invention
The invention relates to a bow, for example a sports or hunting bow or a crossbow.
2. Description of the Related Art
The principle common to the aforementioned pieces of sports or hunting equipment is that an archer draws a string by means of one or more elastic elements, so-called limbs, and then lets it go. The string here accelerates an arrow in the direction of a target. Modern bows or crossbows have little in common with the examples which are known from history. In particular, the variation in force when the string is drawn has, in the meantime, been adjusted optimally to the envisaged use. Therefore for example the force which has to be applied in order to draw a hunting bow in the first instance increases in relation to the deflection of the string and decreases again as the deflection of the string increases. In other words, in the first instance a comparatively large force is necessary in order to deflect the string even just by small amounts. As deflection increases, the force which acts on the archer's drawing arm decreases, and therefore a comparatively low level of force is required in order to hold the bow in its drawn position. This means that, for example in a hunting situation, the task of the archer aiming with the bow drawn is simplified to a considerable extent. This desired behaviour of the bow is achieved according to the prior art in that the string of the bow is guided on rotatable string pulleys at the ends of the limbs. Connected rigidly to the string pulleys, and thus likewise mounted in a rotatable manner, are the so-called cable pulleys, on which are guided compensating cables which serve for the symmetrical deformation of the limbs and for uniform force distribution. The geometry and method of mounting the string and cable pulleys here determine, in addition to other parameters, essentially the variation in force of the bow. The geometry of the string pulleys and of the cable pulleys can result, in particular, in the string no longer being subjected to any restoring force in the case of an excessively large amount of deflection, and therefore the drawn bow remains in its drawn state even in the cases where the archer lets go of the drawn string. This effect is also referred to by the term “cocking”. Even just a slight action or movement can result in a sudden release of drawing tension from a bow drawn in such a way. Particularly in those cases where there is no arrow placed in position, which could convert the stored energy into kinetic energy, the above described sudden release of drawing tension from the bow may result in parts of the bow, in particular the string, the limbs or even the string or cable pulleys, being destroyed. Fragments flying around here may also be hazardous to, or injure, nearby individuals.
In the case of bows with compensating cables, it should be ensured that the arrow, during acceleration, does not come into contact with a compensating cable since, otherwise, the arrow could be deflected laterally or the compensating cable could also be damaged. In the case of a so-called shoot-through bow, this problem is solved in that the arrow, during shooting, is guided through between the compensating cables. The compensating cables are arranged symmetrically in relation to the plane of the string pulleys, wherein it is also possible, at the same time, to realize a high level of symmetry for the variation in force. It is thus also possible to prevent torsion of the bow as a whole as it is drawn. This is important because the elastic torsion of the bow could be released as the arrow accelerates and have an adverse effect on the following phase of flight of the arrow.
The following text will refer to a type 1 shoot-through bow, if the ends of the compensating cables are fitted on the limbs on one side, i.e. if the first end of a compensating cable runs on a cable pulley and the other end of the compensating cable is fixed on the limb opposite. This type of bow is also referred to, inter alia, as a twin-cam bow. In the case of a type 2 shoot-through bow, the compensating cables, in contrast, are not fastened on the limb; rather, they run over the cable pulleys on both sides of the bow. This is a special embodiment of the twin-cam bow, also known as a binary-cam bow.
For the purpose of avoiding cocking, German patent DE 10 2008 063 388 discloses the practice, for shoot-through bows, of having a deflecting stop strike against a compensating cable. The disadvantage here, however, is that the rotary position of the string pulley at maximum deflection, on account of the compliance of the compensating cable against which the deflecting stop strikes, is given only in the presence of comparatively high tolerance. There is no firmly defined stop, i.e. a precise rotary position of the string pulley in relation to the limb.